Vector control and malaria in humanitarian emergencies: the limitations and the needs
Authors: Christophe Boëte
Journal: The Lancet Global Health (2023)

In normative contexts, malaria control can be considered routine and elimination strategies are well implemented; however, in unstable conditions such as humanitarian emergencies, malaria incidence remains poorly understood. The heterogeneity of humanitarian emergencies leads to context-specific challenges, and controlling malaria in such situations often requires tools with particular qualities, including rapid deployment, adaptability, practicality, and ease of implementation. In The Lancet Global Health, Louisa A Messenger and colleagues1Messenger LA Furnival-Adams J Chan K Pelloquin B Paris L Rowland M Vector control for malaria prevention during humanitarian emergencies: a systematic review and meta-analysis.Lancet Glob Health. 2023; 11: e534-e545Summary Full Text Full Text PDF Scopus (1) Google Scholar report a systematic review and meta-analysis on the effectiveness of vector control interventions for malaria prevention in humanitarian settings. This Article represents a very interesting topic on which there is a scarcity of information, despite the need to establish adequate and efficient intervention policies against malaria in these contexts, a gap that has now been partly filled in the latest WHO guidelines for malaria vector control.2WHOWHO guidelines for malaria.https://apps.who.int/iris/handle/10665/354781Date: 3 June 2022Date accessed: February 17, 2023Google Scholar Some of the limitations of the study by Messenger and colleagues reflect the little data available in the particular context of humanitarian emergencies. Getting accurate data is a major challenge in these contexts,3Anderson J Doocy S Haskew C Spiegel P Moss WJ The burden of malaria in post-emergency refugee sites: a retrospective study.Confl Health. 2011; 5: 17Crossref PubMed Scopus (28) Google Scholar where most assessments are “quick and dirty”.4Boëte C Guardiola M Lasry E Burza S Moriana S Robertson W Needs and challenges in modelling malaria for emergency contexts.Trends Parasitol. 2020; 36: 723-726Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar Only 22 studies of more than 10 000 studies were eligible for inclusion, and all the included studies were only related to chronic emergencies. The fact that included studies were only related to chronic emergencies leaves the question of the efficacy of the current vector control tools against malaria in acute emergencies unresolved. Another limitation lies in the fact that there was only one study of 22 in their analysis in which two interventions (insecticide-treated nets [ITN] and indoor residue spraying [IRS]) were combined. This limitation highlights the difficulties to implement integrated vector management approaches with a combination of different interventions in humanitarian contexts. Today, integrated vector management is the most promising approach against malaria5Beier JC Keating J Githure JI Macdonald MB Impoinvil DE Novak RJ Integrated vector management for malaria control.Malar J. 2008; 7: S4Crossref PubMed Scopus (205) Google Scholar, 6Innovative strategies for vector controlEcology and control of vector-borne diseases.https://www.wageningenacademic.com/doi/book/10.3920/978-90-8686-895-7Date accessed: February 17, 2023Google Scholar because it aims at optimising and rationalising the use of resources and tools for cost-effective and sustainable vector control. Getting answers in acute and complex situations appears to be a challenge. This challenge is made harder when malaria combines with other burdens such as malnutrition,7Ajakaye OG Ibukunoluwa MR Prevalence and risk of malaria, anemia and malnutrition among children in IDPs camp in Edo State, Nigeria.Parasite Epidemiol Control. 2019; 8e00127PubMed Google Scholar communicable diseases, and loss of homes. Such situations undeniably call for active coordination between the actors of emergency relief and assistance from non-governmental organisations, UN bodies, or governmental institutions. Obtaining demographic, epidemiological, and entomological indicators to determine the vector control tools that can easily be deployed, adaptable, and easy to implement4Boëte C Guardiola M Lasry E Burza S Moriana S Robertson W Needs and challenges in modelling malaria for emergency contexts.Trends Parasitol. 2020; 36: 723-726Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar would indeed be a major asset. In particular, this identification would inform a choice between a strategy that is considered less effective but that can be quickly implemented and a strategy more efficacious requiring more time and delay to be put in place. Messenger and colleagues1Messenger LA Furnival-Adams J Chan K Pelloquin B Paris L Rowland M Vector control for malaria prevention during humanitarian emergencies: a systematic review and meta-analysis.Lancet Glob Health. 2023; 11: e534-e545Summary Full Text Full Text PDF Scopus (1) Google Scholar conclude that ITNs appear to be the most efficient tools to deploy in chronic humanitarian emergencies against Plasmodium falciparum and Plasmodium vivax. This conclusion corroborates results from a Delphi survey exploring expert opinion on the use of existing tools against malaria within the emergency context, which aimed for a better understanding of their attitude towards emerging and innovative tools.8Boëte C Burza S Lasry E Moriana S Robertson W Malaria vector control tools in emergency settings: what do experts think? Results from a DELPHI survey.Confl Health. 2021; 15: 93Crossref PubMed Scopus (2) Google Scholar The low certainty evidence of several other strategies, such as insecticide-treated plastic sheeting, tarpaulin, or blankets requires proper evaluation with entomological and epidemiological endpoints as well as the constraints and advantages related to their deployment and use in acute emergency situations. Overall, most people affected by humanitarian emergencies live in malaria endemic areas and the vector control toolbox is still too often lacking context-specific and properly evaluated tools. Although novel tools, such as attractive targeted sugar baits9Eisele TP Kleinschmidt I Sarrassat S et al.Attractive targeted sugar bait phase III trials in Kenya, Mali, and Zambia.Trials. 2022; 23: 640Crossref PubMed Scopus (3) Google Scholar or spatial repellents10Ochomo EO Gimnig JE Bhattarai A et al.Evaluation of the protective efficacy of a spatial repellent to reduce malaria incidence in children in western Kenya compared to placebo: study protocol for a cluster-randomized double-blinded control trial (the AEGIS program).Trials. 2022; 23: 260Crossref PubMed Scopus (8) Google Scholar are currently being tested in phase 3 trials, these trials are done in non-emergency settings only. Apart from testing the already existing tools to ensure robust scientific evidence about their efficacy in a variety of emergency settings, it is essential to consider the need for redesigning condition-specific, tailor-made vector control tools and deployment packages in humanitarian emergencies (chronic or acute) whose efficacy is backed by epidemiological evidence—a major criterion for professionals working on malaria vector control in humanitarian settings. I declare no competing interests. Vector control for malaria prevention during humanitarian emergencies: a systematic review and meta-analysisStudy findings strengthen and support WHO policy recommendations to deploy insecticide-treated nets during chronic humanitarian emergencies. There is an urgent need to evaluate and adopt novel interventions for malaria control in the acute phase of humanitarian emergencies. Full-Text PDF Open Access